I know jack crap about fertilizer, but shouldn't this plant have been farther from residential areas?
Ammonium nitrate is used in fertilizer because it is a very good oxidant. Plants need oxygen to grow... Just like fires need oxygen to grow. They say ammonium nitrate in like, ever movie where someone makes a makeshift bomb.
Yeah, the vicinity of the plant to the residential areas was the first thing I thought of but look at that blast radius. I think a lot of the fatalities were from people who went to watch the fire and didn't realize it was about to go boom boom.